JS client does not support polymorphic return types

In the generated constructFromObject functions, the descriminator property is ignored, which means that an instance of the abstract superclass is created. For example, if I have this in my swagger.yaml:

Vehicle:
  type: "object"
  required:
  - "vehicleType"
  discriminator: "vehicleType"
  properties:
    vehicleType:
      type: "string"

Car:
  allOf:
  - $ref: "#/definitions/Vehicle"
  - type: "object"
    required:
    - "vehicleType"
    properties:
      vehicleType:
        type: "string"

Bicycle:
  allOf:
  - $ref: "#/definitions/Vehicle"
  - type: "object"
    required:
    - "vehicleType"
    properties:
      vehicleType:
        type: "string"

then, according to my understanding of how it should work, if the vehicleType is "Car", then a new Car instance should be generated, and if vehicleType is "Bicycle", a new Bicycle instance should be generated.

Currently, all I get is a new Vehicle instance.

Start with the generated constructFromObject functions and the Vehicle/Car/Bicycle schema example in the issue. Trace how the discriminator field is handled when constructing a JavaScript client model. Done means vehicleType selects a Car or Bicycle instance instead of always creating Vehicle, with the behavior verified using the example schema.